A New and Simple Three-Phase Thyristor Inverter for Variable Frequency Operation

A new three-phase inverter circuit is described and analyzed for the condition of an inductive load. The circuit does not require an auxiliary supply or any auxiliary thyristors to assist commutation. All commutation capacitors are placed across the dc side but are used in the same way as capacitors that are normally used for ac side commutation. The output voltage of the inverter is a quasi sine wave controlled by a simple firing circuit. The author was a visiting Research Fellow with the Department of Electrical Engineering and Electronics, the University of Manchester Institute of Science and Technology, Manchester, England.